Electrical utilities monitor the electrical energy consumption of customers through electricity meters. Modern electricity meters typically include numerous solid state electronics components and associated electronic devices including sensor devices, data processors, microprocessors, memory devices, clocks, and communications devices. These electronic devices are used for various purposes within the electricity meter, including consumption detection, consumption calculation, data storage, and automatic meter reading (AMR) communications. In association with these electronic devices, the electricity meters also include a power supply configured to provide DC power to the electronic devices.
A typical onboard power supply utilized in electricity meters is a wide range switching power supply. A single wide range switching power supply may supply the power for both the metering/data acquisition hardware and the communications hardware. Switching power supplies store DC energy in hold-up capacitors. The DC energy stored in hold-up capacitors is typically used to sustain the operation of the meter for some limited amount of time in the event of a power-down event. For example, holdup capacitors may be configured to provide DC power to the microprocessor until the non-volatile memory write cycle is completed (approx. 400 mS) during power outages. The power provided from the capacitor for this short amount of time allows for the recording of energy consumption data which would otherwise be lost in the event of a power outage. Holdup capacitors may also be used in the event of a power outage to power the communications hardware (e.g., AMR devices) such that energy consumption data may be still be transmitted by the communications hardware in the moments immediately following a power outage.
AMR and other communications devices present a significant DC load to the power supply. The amount of power used by the AMR device affects the strength of the output signal transmitted from the AMR device. In particular, when more power is used by the AMR device, the associated output signal is stronger. When less power is used by the AMR device, the associated output signal is weaker. In many situations, the amount of power used by the AMR device presents an undesirable drain on the power supply. Examples of these situations include low service voltages, high temperatures, meter power-up and meter power-down.
Electricity meters are often designed for worst case operating conditions related to service voltages and temperatures for all markets where the meters will be used. In particular, current electricity meters are designed to deliver full DC power to AMR devices under the worst case field conditions, including lowest service voltages and highest operating temperatures. This design philosophy typically leads to a high level of the electrical components within the electricity meter, resulting in a more expensive meter. For example, current electricity meters often utilize holdup capacitors that are sufficiently large to guarantee safe storage and transmission of billing information during power outages, regardless of whether the electricity meter is used in a low service voltage market (e.g., between 70 Vrms and 96 Vrms) or a high service voltage market (e.g., between 96 Vrms and 576 Vrms).
The high power requirements of the AMR and other communications devices may present other issues in addition to over-design of the electricity meter. For example, during initial meter power up at low line voltages, the DC power consumed by the AMR device can increase the start-up time for the electronics associated with metering. These longer start-up times can result in lost data related to electrical energy consumption by the customer. While only a small amount of energy consumption data may be lost for each start up, the lost data may add up over time as power outages continue to occur with subsequent meter power ups. The lost data from numerous meter power ups resulting in significant lost revenues to the electrical utility.
In view of the foregoing, it would be advantageous to provide an electricity meter with less expensive electronics. Additionally, it would be advantageous to provide a power supply for an electricity meter capable of faster meter start-up times, thus reducing lost revenues over the life of the meter.